This invention relates generally to a method for determining the fuel injection timing for an internal combustion engine and, more particularly, to a method for determining the fuel injection timing for an internal combustion engine during starting.
A diesel engine achieves combustion by injecting fuel that vaporizes into the hot air of an engine cylinder. However, during cold starting conditions, the air loses much of its heat to the cylinder walls making engine starting difficult. For example, if fuel is injected into the cylinder too soon, the cold fuel cools the air charge preventing combustion temperatures from occurring. If fuel is injected too late, much of the fuel will not used in the combustion.
The maximum cylinder temperature and pressure should occur at Top Dead Center (TDC). Therefore, it is desirable to inject fuel into the cylinder slightly before TDC where air temperature is at a maximum to improve combustibility. As engine speed increases, the fuel injection timing should be increased to achieve optimum combustion.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention, a method is disclosed for controlling the timing at which fuel is to be injected. In response to engine speed and temperature, a desired timing signal is produced. The desired timing angle represents when the start of injection is to occur in order to cause combustion at substantially Top Dead Center (TDC). The timing signal additionally accounts for a predetermined ignition delay from the time that fuel is injected to the start of combustion.